L6 - Introduction to Drosophila Flashcards
Positives of mice as animal models?
Good genetics
Well established model
Negatives of mice as animal models?
Expensive
Slow reproductive cycle
Ethical restrictions/home office
Positives of chicks as animal models?
Accessible embryology
Low cost
Negatives of chicks as animal models?
No genetics
Ethical restrictions/home office
Positives of zebrafish as animal models?
Accessible embryology
Reasonable low cost
Negatives of zebrafish as animal models?
Genetics problematic
Ethical restrictions
Positives of drosophila as animal models?
Accessible embryology and adult developmental stages Very low cost Fast reproductive cycle Good genetics No ethical restrictions
Negatives of drosophila as animal models?
Not a vertebrate
Kept at live stocks
Drosophila life cycle
Live around 60 days
Life cycle
- 10 days at 25oC
- 21 days at 18oC
Drosophila life cycle stages
- Fertilised egg (cleavage)
- Syncytial blastoderm (gastrulation)
- Embryo (hatching)
- Larva
- Pupa (metamorphis)
- Adult fly
Drosophila history - 1910
Morgan discovered a white eyed fly
Drosophila history - 1913
Sturtevant constructed first genetic map - genes arranged in a linear order
Drosophila history - 1914
Bridges showed that chromosomes must contain genes
Drosophila history - 1927
Muller showed that X-rays cause mutations and chromosomal rearrangements
Drosophila history - 1980
Christiane Nüsslein-Volhard and Eric Wischaus undertook a saturation mutagenesis to identify genes involved in development and patterning of larval cuticle
Drosophila history - 1980s
Technical and methological advances
- P-element transformation - transgenics
- Enhancer trap - promoter trapping
- Gal4/UAS - gene misexpression
- FLP/FRT - clonal mutant analysis
- RNAi - ex vivo and in vivo
- ‘omic’ technologies - genome, transcriptome, proteome
Drosophila history - 2014
Drosophila melanogaster genome release 6
- 143 million bp
- 137.6 million bp on the 7 chromosome arms
- Remaining gaps of around 1.5Mbp all in heterochromatin regions
Drosophila melanogaster ptp61F - a tyrosine phosphatase sequence was compared to?
Drosophila simulans - 3.4 my Drosophila erecta - 6.8 my Drosophila ananassae - 9.5 my Drosophila pseudoobscura - 23.7my Drosophila virilis - 34.5my Protein encoding exons are conserved – don’t diverge as quickly
How many offspring can flies produce in roughly 2 weeks?
Around 200
How is Drosophila courtship passed down generations?
Strong reproducible behaviour Genetically encoded (not learned)
What are some examples of Drosophila courtship?
Orientation Tapping Wing vibration Licking Attempted copulation
In flies what does the testes consist of?
Consist of hub cells
Stem cells located adjacent to hub
Cells further away differentiate
What do Hub cells secrete?
Unpaired - JAK/STAT pathway ligand
Oogenesis
Females only need to mate once in lifetime
Seminal receptacle stores sperm
Eggs drilled into food when laid
How are stem cells maintained in the embryo?
4x incomplete cystoblast mitotic divisions Selection of future oocyte - Nurse cells - endo-reduplication - Oocyte - Diploid nucleus - Meiotic recombination
What does the fly sperm fuse with?
The female pro-nucleus
What is the function of nurse cells?
They are support cells
Supply egg with protein, yolk, RNAs - maternal contributions
How are the maternal contributions from nurse cells transferred into oocyte?
Transferred into developing oocyte via cytoplasmic dumping
Occurs via ring canals
How are nurse cells replicated?
Endo-reduplication
- DNA replication without cytokinesis
Many copies of the genome
What are polytene chromosomes?
All sister chromatids lie together Bands - little gene activity Interbands - active genes Puffs - extremely active gene 5000 bands - each 22 kb
Microtubule transport is used to?
Aid subcellular localisation
- Minus and plus ended motors
- Glue anchors them in position
What is chorin?
Egg shell
Secreted by the follicle cells
What is the vitelline membrane?
Hydrophobic
Protects from drying out
What does early development via nuclear divisions look like?
Nucleus replicates DNA with no cell division
Uses maternal material form nurse cells
What happens after the 14th nuclear division?
Membranes grow from outside and each nucleus gets pinched of into its own cell